Securities In An Unrealized Loss Position Securities In An Unrealized Loss Position (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	$ 2,971,800	$ 1,536,923
Gross Unrealized Losses	79,075	35,018
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	39,338	39,812
Gross Unrealized Losses	4,384	1,651
Preferred stocks | Noninvestment Grade Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of securities	3
Aggregate fair value of securities in a continuous unrealized loss position	39,000
Gross Unrealized Losses	4,000
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	77,610	46,725
Gross Unrealized Losses	5,360	707
Common stocks | Noninvestment Grade Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of securities	6
Aggregate fair value of securities in a continuous unrealized loss position	78,000
Gross Unrealized Losses	$ 5,000